Explainer
JPG vs PNG: Which Format Is Best for PDF Pages?
When you convert a PDF to images, the format you pick affects sharpness, file size and where the images can be used. This guide explains the real differences between JPG and PNG and gives you a simple rule for choosing.
Quick answer: choose JPG for scanned pages, photos and anything you want to share or upload with small file sizes. Choose PNG for pages that are mostly text, tables, charts, diagrams or slides when you want the crispest edges, or when you will edit the images further.
First, what happens when a PDF becomes an image?
Most PDFs store text and shapes as vectors: mathematical descriptions that stay sharp at any zoom level. Images, on the other hand, are rasters: fixed grids of coloured pixels. Converting a PDF page to JPG or PNG means "rendering" it into pixels at a chosen resolution.
Resolution decides how much detail is captured; the image format decides how those pixels are stored and compressed. That second part is where JPG and PNG differ.
How JPG works
JPG (or JPEG, after the Joint Photographic Experts Group that created it) uses lossy compression. It splits the image into small blocks and discards fine detail that the human eye is unlikely to notice, especially subtle colour variations. The result is a dramatically smaller file.
This approach is excellent for photographs and scans, where smooth gradients and natural textures hide the compression. It is less suited to hard edges: around small black text on a white background, aggressive JPG compression can leave faint grey speckles or "ringing", known as compression artefacts. At high quality settings these artefacts are minor; at low settings they become obvious.
JPG has two other characteristics worth knowing: it does not support transparency, and every time you edit and re-save a JPG, it is compressed again and loses a little more detail.
How PNG works
PNG (Portable Network Graphics) uses lossless compression. It finds repeating patterns in the pixel data and stores them more efficiently, but it never throws information away: decompress a PNG and you get back exactly the pixels you saved.
Lossless compression is extremely efficient for images with large areas of flat colour and sharp edges, which describes a typical page of text, a spreadsheet, a bar chart or a slide. For photographs, however, PNG files become very large because natural images have few exactly repeating patterns.
PNG also supports transparency, and you can open, edit and re-save a PNG as many times as you like without any loss.
Side-by-side comparison
| Feature | JPG | PNG |
|---|---|---|
| Compression | Lossy (discards some detail) | Lossless (keeps every pixel) |
| Typical file size for a text page | Small | Small to medium |
| Typical file size for a photo page | Small | Large (often several times bigger) |
| Sharpness of small text and thin lines | Very good at high quality, can blur at low quality | Excellent |
| Transparency | No | Yes |
| Quality after repeated editing | Degrades with each re-save | No degradation |
| Compatibility | Universal | Universal |
Which format for which job?
Choose JPG for…
- Scanned documents. Scans already contain paper texture and noise, which JPG compresses efficiently with no visible downside.
- Brochures, magazines and photo-heavy pages. PNG files of these pages can be huge for no visible gain.
- Email and chat. Smaller files send faster and stay under attachment limits.
- Uploading to forms and portals with strict size limits.
- Social media. Platforms such as Instagram and Facebook recompress uploads as JPG anyway.
Choose PNG for…
- Text-heavy pages that people will read on screen or zoom into.
- Charts, diagrams, tables and slides with flat colours and fine lines.
- Images you will edit further (annotating, cropping or combining in a design tool), because PNG won't lose quality on each save.
- OCR (text recognition). Clean, artefact-free edges can help OCR software recognise characters more accurately.
A note on file size
It is a common myth that PNG is always bigger than JPG. For a clean page of black text on white, a PNG can be about the same size as a high-quality JPG, and sometimes smaller. The gap widens dramatically for pages containing photographs or gradients, where PNG files can be many times larger.
If you are unsure, try both on a few representative pages and compare. With MyImageNinja you can switch between PNG and JPG in Export & Settings → Images (ZIP) and export again in seconds, since the pages are already rendered.
What about WebP, TIFF and others?
- WebP is a modern web format that supports both lossy and lossless compression with smaller files than JPG or PNG. It is great for websites, but some older software and many upload forms still expect JPG or PNG.
- TIFF is popular in professional printing and archiving and can store multiple pages in one file, but files are large and browsers can't display it.
- GIF is limited to 256 colours, which makes it unsuitable for most document pages.
For PDF pages that need to work everywhere, JPG and PNG remain the safest choices.
The rule of thumb
Ask one question: "Is this page mostly photos or mostly text and graphics?" Photos and scans → JPG. Text, charts and diagrams → PNG. And if file size is your main concern, JPG is almost always the smaller option.